Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
Consequently, there are different types of alveoli (plural) found throughout the human body. However, alveoli are usually used to describe the small air sacs of the lungs of mammals, and are therefore known more specifically as the pulmonary alveoli. The pulmonary alveolus is a sac roughly 0.2 to 0.5 mm in diameter. These alveoli are located at the ends of air passageways in the lungs.